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Journal articles on the topic 'Reaction enthalpies'

Author: Grafiati

Published: 4 June 2021

Last updated: 10 February 2022

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1

Zhao, Yusheng, and Galen J. Suppes. "Computational study on reaction enthalpies of urethane-forming reactions." Polymer Engineering & Science 55, no. 6 (April 15, 2015): 1420–28. http://dx.doi.org/10.1002/pen.24086.

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2

Milenković, Dejan, Jelena Đorović, Edina Avdović, Žiko Milanović, and Marko Antonijević. "THERMODYNAMIC AND KINETIC INVESTIGATION OF ANTIRADICAL POTENTIAL OF CYANIDIN." Journal of the Serbian Society for Computational Mechanics, Special (June 1, 2020): 85–95. http://dx.doi.org/10.24874/jsscm.2020.01.08.

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In the present paper, M05-2X/6-311+G(d,p) level of theory was used to investigate antiradical activity of cyanidin towards highly damaging radical species (.OH, .OCH3, .OOH and .OOCH3). The applied method successfully reproduces the values of reaction enthalpies (ΔHBDE, ΔHIP, and ΔHPA). These parameters are important to determine which of the mechanisms are preferred. Reaction enthalpies related to the antioxidant mechanisms of the investigated species were calculated in water and DMSO. The enthalpies of reactions indicate the preferred radical scavenging mechanisms in polar (water) and polar aprotic (DMSO) solvents. Single- electron transfer followed by proton transfer (SET-PT) is not a favorable reaction pathway under any conditions. Both remaining mechanisms, HAT and SPLET, are suitable for the reaction of cyanidin with •OH and •OCH3 in all solvents under investigation. On the other hand, in the reaction of cyanidin with •OOH and •OOCH3, the SPLET mechanism is possible in both solvents. Simulation of the reaction of the cyanidin anion with the hydroxy radical confirmed that position 3` of Cy‒O- is the most suitable for reaction with •OH through electron transfer mechanism (ET) in both solvents.

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3

Lording, William J., Alan D. Payne, Tory N. Cayzer, Michael S. Sherburn, and Michael N. Paddon-Row. "A Combined Computational–Experimental Study of the Kinetics of Intramolecular Diels–Alder Reactions in a Series of 1,3,8-Nonatrienes." Australian Journal of Chemistry 68, no. 2 (2015): 230. http://dx.doi.org/10.1071/ch14430.

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Activation enthalpies for a series of five 1,3,8-nonatriene intramolecular Diels–Alder (IMDA) reactions involving substrates 1–5 have been determined experimentally and Singleton’s natural abundance method has been employed to determine kinetic isotope effects in the IMDA reaction of fumarate 3. The activation enthalpies for the IMDA reactions of the systems possessing a –CH2OCH2– diene/dienophile tether are significantly smaller than their counterparts possessing the –CH2OC(=O)– tether. The experimental activation enthalpies have been used to benchmark computed values from four model chemistries, namely two density functional theory functionals, B3LYP and M06-2X, and two generally very accurate composite ab initio wave function methods, CBS-QB3 and G4(MP2). G4(MP2) outperformed the computationally more expensive CBS-QB3 method, but the vastly cheaper M06-2X/6-31G(d)//B3LYP/6-31G(d) method was sufficiently accurate to be the recommended method of choice for calculating activation parameters. Experimental 2H kinetic isotope effects for the IMDA reaction of fumarate 3 confirmed the computational predictions that this Diels–Alder reaction is concerted but asynchronous.

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4

Schnell, Sondre K., Ragnhild Skorpa, Dick Bedeaux, Signe Kjelstrup, Thijs J. H. Vlugt, and Jean-Marc Simon. "Partial molar enthalpies and reaction enthalpies from equilibrium molecular dynamics simulation." Journal of Chemical Physics 141, no. 14 (October 14, 2014): 144501. http://dx.doi.org/10.1063/1.4896939.

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5

Rhodes, Christopher J., Thuy T. Tran, Philip Denton, and Harry Morris. "Rationalisation of the activities of phenolic (vitamin E-type) antioxidants." Spectroscopy 17, no. 4 (2003): 753–62. http://dx.doi.org/10.1155/2003/607917.

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Using Transition-State Theory, experimental rate constants, determined over a range of temperatures, for reactions of vitamin E type antioxidants are analysed in terms of their enthalpies and entropies of activation. It is further shown that computational methods may be employed to calculate enthalpies and entropies, and hence Gibbs Free Energies, for the overall reactions. Within the Linear Free Energy Relationship (LFER) assumption, that the Gibbs Free Energy of activation is proportional to the overall Gibbs Free Energy change for the reaction, it is possible to rationalise, and even to predict, the relative contributions of enthalpy and entropy for reactions of interest, involving potential antioxidants.

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6

Herman, Zdeněk, and Rudolf Zahradník. "Calculation of reaction energies for ion-molecule processes of first-row ions and their hydrides." Collection of Czechoslovak Chemical Communications 54, no. 11 (1989): 2910–18. http://dx.doi.org/10.1135/cccc19892910.

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Reaction energies calculated by quantum chemical methods are compared with reaction enthalpies obtained on the basis of experimental heats of formation. Fifty six ion-molecule reactions (X+ + H2, XH+ + H2, where X is boron, carbon, or nitrogen, and reactions involving C2H2.+, C2H4.+, and C2H6.+) have been arranged into structurally related sets. Moreover, nine processes important in connection with the C2H2 formation in interstellar clouds are treated.

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7

Leinemann, Inga, Kristi Timmo, Maarja Grossberg, Tiit Kaljuvee, Kaia Tõnsuaadu, Rainer Traksmaa, Mare Altosaar, and Dieter Meissner. "Reaction enthalpies of Cu2ZnSnSe4 synthesis in KI." Journal of Thermal Analysis and Calorimetry 119, no. 3 (January 31, 2015): 1555–64. http://dx.doi.org/10.1007/s10973-014-4339-5.

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8

Schmidt, Reinhard, and Matthias Schütz. "Determination of reaction volumes and reaction enthalpies by photoacoustic calorimetry." Chemical Physics Letters 263, no. 6 (December 1996): 795–802. http://dx.doi.org/10.1016/s0009-2614(96)01274-2.

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9

Domingo, Luis R., Nivedita Acharjee, and Haydar A. Mohammad-Salim. "Understanding the Reactivity of Trimethylsilyldiazoalkanes Participating in [3+2] Cycloaddition Reactions towards Diethylfumarate with a Molecular Electron Density Theory Perspective." Organics 1, no. 1 (October 16, 2020): 3–18. http://dx.doi.org/10.3390/org1010002.

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A Molecular Electron Density Theory (MEDT) study is presented here for [3+2] cycloaddition (32CA) reactions of three trimethylsilyldiazoalkanes with diethyl fumarate. The presence of silicon bonded to the carbon of these silyldiazoalkanes changes its structure and reactivity from a pseudomonoradical to that of a zwitterionic one. A one-step mechanism is predicted for these polar zw-type 32CA reactions with activation enthalpies in CCl4 between 8.0 and 19.7 kcal·mol−1 at the MPWB1K (PCM)/6-311G(d,p) level of theory. The negative reaction Gibbs energies between −3.1 and −13.2 kcal·mole−1 in CCl4 suggests exergonic character, making the reactions irreversible. Analysis of the sequential changes in the bonding pattern along the reaction paths characterizes these zw-type 32CA reactions. The increase in nucleophilic character of the trimethylsilyldiazoalkanes makes these 32CA reactions more polar. Consequently, the activation enthalpies are decreased and the TSs require less energy cost. Non-covalent interactions at the TSs account for the stereoselectivity found in these 32CA reactions involving the bulky trimethylsilyl group.

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10

Najafi, Meysam, Mohammad Najafi, and Houshang Najafi. "DFT/B3LYP Study of the Substituent Effects on the Reaction Enthalpies of the Antioxidant Mechanisms of Sesamol Derivatives in the Gas phase and water." Canadian Journal of Chemistry 90, no. 10 (October 2012): 915–26. http://dx.doi.org/10.1139/v2012-087.

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In this paper, the study of various ortho and meta–substituted Sesamol derivatives is presented. The reaction enthalpies related to three antioxidant action mechanisms HAT, SET–PT, and SPLET for substituted Sesamols, have been calculated using the DFT/B3LYP method in gas phase and water. Calculated results show that electron-withdrawing substituents increase the bond dissociation enthalpy (BDE), ionization potential (IP), and electron transfer enthalpy (ETE), while electron-donating ones cause a rise in the proton dissociation enthalpy (PDE) and proton affinity (PA). In the ortho position, substituents show a larger effect on reaction enthalpies than in the meta position. In comparison with the gas phase, water attenuates the substituent effect on all reaction enthalpies. In the gas phase, BDEs are lower than PAs and IPs, i.e., HAT represents the thermodynamically preferred pathway. On the other hand, the SPLET mechanism represents the thermodynamically favored process in water. Results show that calculated enthalpies can be successfully correlated with Hammett constants (σm) of the substituted Sesamols. Furthermore, calculated IP and PA values for substituted Sesamols show linear dependence on the energy of the highest occupied molecular orbital (EHOMO).

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11

Alvarez, Alfredo Maestre, Nicole Morel-Desrosiers, and Jean-Pierre Morel. "Interactions between cations and sugars. III. Free energies, enthalpies, and entropies of association of Ca2+, Sr2+, Ba2+, La3+, Gd3+ with D-ribose in water at 25 °C." Canadian Journal of Chemistry 65, no. 11 (November 1, 1987): 2656–60. http://dx.doi.org/10.1139/v87-439.

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The standard enthalpies of transfer of ribose and arabinose from water to aqueous solutions of electrolytes (CaCl2, SrCl2, BaCl2, LaCl3, and GdCl3) have been measured at 25 °C. A method is described to calculate from these data the equilibrium constant and the enthalpy for the association between the cations and the complexing isomers of ribose. Mean values relative to these isomers are given: the constants vary from 2.0 to 4.3 and the enthalpies from −5.9 to −17.9 kJ mol−1 for the different cations studied. The thermodynamic properties of association are not related to the size nor to the charge of the complexed cation in a simple way. On the other hand, the enthalpies of reaction are linearly correlated to the entropies of reaction.

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12

Cagardová, Denisa, Martin Michalík, Erik Klein, Vladimír Lukeš, and Zoran Marković. "DFT and ab initio calculations of ionization potentials, proton affinities and bond dissociation enthalpies of aromatic compounds." Acta Chimica Slovaca 12, no. 2 (October 1, 2019): 225–40. http://dx.doi.org/10.2478/acs-2019-0032.

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Abstract Theoretical study of phenol, thiophenol, benzeneselenol, aniline and their para-amino and paranitro derivatives is presented. Neutral molecules, their deprotonated forms, neutral radicals, and radical cations were studied using three Density Functional Theory (DFT) functionals as well as combined DFT and ab initio G4 method in order to calculate the N—H, O—H, S—H, and Se—H bond dissociation enthalpies (BDE), proton affinities of corresponding anions (PA) and ionization potentials (IP) of studied compounds. These quantities represent fundamental reaction enthalpies related to the radical scavenging action of primary antioxidants. Calculated values were compared with available experimental data to assess applicability of the computational approaches employed. M06-2X/6-311++G(d,p) and G4 methods showed the best agreement with the available experimental gas-phase reaction enthalpies.

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13

Ooi, N., James B. Adams, and Uttam Singisetti. "Reaction enthalpies as selection criteria for tribological coatings." physica status solidi (b) 239, no. 1 (September 2003): 44–47. http://dx.doi.org/10.1002/pssb.200303237.

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14

Arcus, Vickery L., and Adrian J. Mulholland. "Temperature, Dynamics, and Enzyme-Catalyzed Reaction Rates." Annual Review of Biophysics 49, no. 1 (May 6, 2020): 163–80. http://dx.doi.org/10.1146/annurev-biophys-121219-081520.

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We review the adaptations of enzyme activity to different temperatures. Psychrophilic (cold-adapted) enzymes show significantly different activation parameters (lower activation enthalpies and entropies) from their mesophilic counterparts. Furthermore, there is increasing evidence that the temperature dependence of many enzyme-catalyzed reactions is more complex than is widely believed. Many enzymes show curvature in plots of activity versus temperature that is not accounted for by denaturation or unfolding. This is explained by macromolecular rate theory: A negative activation heat capacity for the rate-limiting chemical step leads directly to predictions of temperature optima; both entropy and enthalpy are temperature dependent. Fluctuations in the transition state ensemble are reduced compared to the ground state. We show how investigations combining experiment with molecular simulation are revealing fundamental details of enzyme thermoadaptation that are relevant for understanding aspects of enzyme evolution. Simulations can calculate relevant thermodynamic properties (such as activation enthalpies, entropies, and heat capacities) and reveal the molecular mechanisms underlying experimentally observed behavior.

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15

Ma, Shao Mei, Sheng Fu Wu, Zeng Wei Huang, An Ping Liao, and Ai Qun Yuan. "Synthesis and Standard Molar Formation Enthalpy of Plate Shape NaZnPO₄·H₂O." Applied Mechanics and Materials 121-126 (October 2011): 175–80. http://dx.doi.org/10.4028/www.scientific.net/amm.121-126.175.

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Plate shape NaZnPO4·H2O was synthesized by solid-state reaction at low temperature and characterized by X-Ray Diffraction, Scanning electron microscope and elemental analysis. Thermochemical study was performed with an isoperibol solution calorimeter. Based on Hess’s law, thermochemical cycl was designed to determine the dissolution enthalpies of reactants and products using a solution-reaction isoperibol calorimeter at 298.15 K, and the molar reaction enthalpy was calculated on the basis of above dissolution enthalpies. The results show that the obtained product is plate shape NaZnPO4·H2O. The standard molar formation enthalpy of the NaZnPO4·H2O is ΔfHm [NaZnPO4·H2O,s]= -1967.18 ± 0.69 kJ•mol-1.

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16

Da Silva, Manuel A. V. Ribeiro, and M. Luisa C. C. H. Ferrāo. "Standard enthalpies of formation of tris(β-diketonate)manganese(III) complexes: the mean (Mn—O) bond-dissociation enthalpies." Canadian Journal of Chemistry 66, no. 4 (April 1, 1988): 651–54. http://dx.doi.org/10.1139/v88-112.

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The standard molar enthalpies of formation of the crystalline complexes of manganese(III) with 1-phenyl-1,3-butanedione (HBZAC) and 2,2,6,6-tetramethyl-3,5-heptanedione (HDPM) were determined, at 298.15 K, by solution–reaction calorimetry:[Formula: see text]The mean molar bond-dissociation enthalpies, [Formula: see text], were derived as 163 ± 10 kJ mol−1 and 170 ± 10 kJ mol−1, respectively.

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17

McGilp, John F. "Alloying and entropy effects in predicting metal/compound–semiconductor interface reactivity." Journal of Materials Research 2, no. 4 (August 1987): 516–23. http://dx.doi.org/10.1557/jmr.1987.0516.

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A previous bulk thermodynamic model, which used enthalpies of compound and alloy formation to predict metal/compound–semiconductor interface reactivity, is extended to include entropy. It is shown that, for most metals on CdTe, GaAs, GaSe, InP, and MoS2, solid-state reactions are energetically favored up to semiconductor dissociation temperatures and, consequently, entropy effects are minimal. Gold and silver, with their small enthalpies of metal–semiconductor anion compound formation, can be exceptions. Even here, the results for gold/III–V systems favor solid-state reaction at room temperature, but at higher temperatures entropy drives the reaction via vapor-phase production of the group V element. The binary phase bulk thermodynamic model is not sufficient to predict absolute reactivity, but can rank the reactivity of the various metal–semiconductor combinations successfully, as long as possible alloy formation is included. It is suggested that the limitations of the model are due to the specific effects of the interface.

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18

Zhou, Chengshang, Yunhe Gao, Robert C. Bowman, Jingxi Zhang, Huang Liu, Pei Sun, and Zhigang Zak Fang. "A high throughput dynamic method for characterizing thermodynamic properties of catalyzed magnesium hydrides by thermogravimetric analysis." Physical Chemistry Chemical Physics 23, no. 28 (2021): 15374–83. http://dx.doi.org/10.1039/d1cp02498a.

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19

Toušek, Jaromír, Jaro Komenda, and Ulrich Hess. "Study of the Electrochemically Initiated Cyanomethylation of Azomethines by Means of the MNDO and AM1 Semiempirical Methods." Collection of Czechoslovak Chemical Communications 60, no. 12 (1995): 2028–38. http://dx.doi.org/10.1135/cccc19952028.

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The semiempirical methods (MNDO and AM1) have been used in the quantum chemical study of electrochemically initiated cyanomethylation of azomethines. Reaction steps leading to the main product of the studied reaction, β-aminonitrile, have been described. The stationary points on the reaction path have been found and the activation enthalpies of reaction steps have been determined. Three possible mechanisms for the abstraction of a proton from acetonitrile have been described (by azomethine radical anion, by β-aminonitrile anion, and by hydrogenated azomethine anion). At the MNDO level, the abstraction of a proton by azomethine radical anion has the highest activation enthalpy (∆H = 197 kJ mol-1) and the abstraction of a proton by hydrogenated azomethine anion has the lowest activation enthalpy (∆H = 146 kJ mol-1). The activation enthalpy of the next reaction step (the reaction of acetonitrile anion with azomethine) is low compared to the activation enthalpies of the previous reation steps (∆H= 12 kJ mol-1).

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20

Powell, Kipton J., Paul L. Brown, Robert H. Byrne, Tamás Gajda, Glenn Hefter, Staffan Sjöberg, and Hans Wanner. "Chemical speciation of environmentally significant heavy metals with inorganic ligands. Part 1: The Hg2+– Cl–, OH–, CO32–, SO42–, and PO43– aqueous systems (IUPAC Technical Report)." Pure and Applied Chemistry 77, no. 4 (January 1, 2005): 739–800. http://dx.doi.org/10.1351/pac200577040739.

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This document presents a critical evaluation of the equilibrium constants and reaction enthalpies for the complex formation reactions between aqueous Hg(II) and the common environmental inorganic ligands Cl–, OH–, CO32–, SO42–, and PO43–. The analysis used data from the IUPAC Stability Constants database, SC-Database, focusing particularly on values for 25 °C and perchlorate media. Specific ion interaction theory (SIT) was applied to reliable data available for the ionic strength range Ic < 3.0 mol dm–3. Recommended values of log10βp,q,r° and the associated reaction enthalpies, ∆rHm°, valid at Im = 0 mol kg–1 and 25 °C, were obtained by weighted linear regression using the SIT equations. Also reported are the equations and specific ion interaction coefficients required to calculate log10βp,q,r° values at higher ionic strengths and other temperatures. A similar analysis is reported for the reactions of H+ with CO32– and PO43–. Diagrams are presented to show the calculated distribution of Hg(II) amongst these inorganic ligands in model natural waters. Under typical environmental conditions, Hg(II) speciation is dominated by the formation of HgCl2(aq), Hg(OH)Cl(aq), and Hg(OH)2(aq).

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21

Xing, Guolong, Tingting Yan, Saikat Das, Ling Ye, and Kaiqi Ye. "Charged porous organic frameworks bearing heteroatoms with enhanced isosteric enthalpies of gas adsorption." RSC Advances 8, no. 36 (2018): 20434–39. http://dx.doi.org/10.1039/c7ra12860f.

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22

Rycerz, L., and M. Gaune-Escarda. "Calorimetric Investigation of NdI3-MI Liquid Systems (M = Li, Na, K, Rb, Cs)." Zeitschrift für Naturforschung A 57, no. 3-4 (April 1, 2002): 136–42. http://dx.doi.org/10.1515/zna-2002-3-405.

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The molar enthalpies of mixing, Δmix Hm, of the liquid alkali metal iodide - neodymium iodide binary systems have been measured over the whole composition range at 1068 K with an accuracy of about 6%. The apparatus used was a Calvet - type high - temperature microcalorimeter. In all the systems under investigation the enthalpies of mixing are negative, with minimum values close to −1.1, −4.8, −10.3, −16.2, and −20.0 kJ mol−1 for LiI-NdI3, NaI-NdI3, KI-NdI3, RbI-NdI3, and CsI-NdI3, respectively, at the mole fractions xNdI3 ⋍ 0.30 - 0.40 except the LiI-NdI3 system, where it is at the NdI3-rich compositions. The molar enthalpies of formation ΔformHm at 1068 K for M = Li, Na, K, Rb, and Cs, arising from the reaction 3 MI(l) + NdI3(l), are found to be −4.5, −17.5, −39.1, −59.9, and −73.3 kJmol−1, respectively They are compared with the formation enthalpies determined previously for the (3MCl, NdCl3) and (3MBr,NdBr3) liquid mixtures. These enthalpies become less negative with increase of the radius of the halide ion.

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23

Dorofeeva, Olga V., and Oxana N. Ryzhova. "Gas-Phase Enthalpies of Formation and Enthalpies of Sublimation of Amino Acids Based on Isodesmic Reaction Calculations." Journal of Physical Chemistry A 118, no. 19 (May 5, 2014): 3490–502. http://dx.doi.org/10.1021/jp501357y.

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24

Lee, E. P. F., J. M. Dyke, F. T. Chau, W. K. Chow, and D. K. W. Mok. "Reaction enthalpies and activation energies of two important reactions in flame suppression by CF3Br." Chemical Physics Letters 376, no. 3-4 (July 2003): 465–74. http://dx.doi.org/10.1016/s0009-2614(03)01005-4.

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25

Xu, Hongwu, Alexandra Navrotsky, May D. Nyman, and Tina M. Nenoff. "Octahedral microporous phases Na2Nb2−xTixO6−x(OH)x·H2O and their related perovskites: Crystal chemistry, energetics, and stability relations." Journal of Materials Research 20, no. 3 (March 1, 2005): 618–27. http://dx.doi.org/10.1557/jmr.2005.0100.

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A family of microporous phases with compositions Na2Nb2−xTixO6−x(OH)x⋅H2O (0 ≤ x ≤ 0.4) transform to Na2Nb2−xTixO6−0.5x perovskites upon heating. In this study, we have measured the enthalpies of formation of the microporous phases and their corresponding perovskites from the constituent oxides and from the elements by drop solution calorimetry in 3Na2O·4MoO3 solvent at 974 K. As Ti/Nb increases, the enthalpies of formation for the microporous phases become less exothermic up to x = ∼0.2 but then more exothermic thereafter. In contrast, the formation enthalpies for the corresponding perovskites become less exothermic across the series. The energetic disparity between the two series can be attributed to their different mechanisms of ionic substitutions: Nb5+ + O2− → Ti4+ + OH− for the microporous phases and Nb5+ → Ti4+ + 0.5VO.. for the perovskites. From the calorimetric data for the two series, the enthalpies of the dehydration reaction, Na2Nb2−xTixO6−x(OH)x⋅H2O → Na2Nb2−xTixO6−0.5x + H2O, have been derived, and their implications for phase stability at the synthesis conditions are discussed.

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26

Minh Hue, Nguyen Thi. "THEORETICAL STUDY ON THE REACTION MECHANISM OF CO2 FORMATION FROM ACYLOXY RADICALS." Vietnam Journal of Science and Technology 55, no. 6A (April 23, 2018): 105. http://dx.doi.org/10.15625/2525-2518/55/6a/12370.

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The decomposition mechanism of acyloxy radicals has been studied by the Density Functional Theory (DFT) using B3LYP functional in conjunction with the 6-311++G(d,p) and 6-311++G(3df,2p) basis sets. The potential energy profiles for reaction systems were generally established. Calculated results indicate that the formation of products including hydrocarbon radicals and CO2 molecule is energetically favored. The rate of decomposition increases with the number of carbon in non-cyclic saturated acyloxy radicals. Calculated enthalpies and Gibbs free energies of reactions well agree with experimental values. This study is a contribution to the understanding of the reaction mechanism of decomposition of acyloxy radicals in atmosphere and combustion chemistry.

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27

Michalík, Martin, Peter Škorňa, Vladimír Lukeš, and Erik Klein. "Acidic and alkaline bimolecular hydrolysis of substituted formanilides. Computational analysis and modelling of substitution effects." Acta Chimica Slovaca 10, no. 1 (April 25, 2017): 35–40. http://dx.doi.org/10.1515/acs-2017-0006.

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Abstract In this article, the study of 67 compounds representing various para-, meta- and ortho- substituted formanilides is presented. These molecules and the products of their acidic and alkaline hydrolysis were studied using DFT quantum chemical methods in order to calculate the reaction enthalpies. These enthalpies are correlated with the hydrolysis rate constants, kH, published for the acid-catalysed acyl cleavage bimolecular (AAC2) mechanism and the modified base-catalysed acyl cleavage bimolecular (BAC2) mechanism. The found linear dependences can be used for the prediction of rate constants of non-synthesised formanilide derivatives.

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28

Hector Jr, L. G., S. M. Opalka, G. A. Nitowski, L. Wieserman, D. J. Siegel, H. Yu, and J. B. Adams. "Investigation of vinyl phosphonic acid/hydroxylated α-Al2O3() reaction enthalpies." Surface Science 494, no. 1 (November 2001): 1–20. http://dx.doi.org/10.1016/s0039-6028(01)01387-5.

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29

Asatryan, Rubik, Joseph W. Bozzelli, and John M. Simmie. "Thermochemistry for enthalpies and reaction paths of nitrous acid isomers." International Journal of Chemical Kinetics 39, no. 7 (2007): 378–98. http://dx.doi.org/10.1002/kin.20247.

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30

Martínez-Herrera, Melchor, and Aarón Rojas. "Enthalpies of Formation and Reaction of Two PCBM Fullerene Derivatives." Journal of Physical Chemistry C 115, no. 5 (December 20, 2010): 1541–47. http://dx.doi.org/10.1021/jp108654x.

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31

Kretzschmar, K., and K. W. Hoffmann. "Reaction enthalpies during the curing oe epoxy resins with anhydrides." Thermochimica Acta 94, no. 1 (October 1985): 105–12. http://dx.doi.org/10.1016/0040-6031(85)85250-3.

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32

Školáková, Andrea, Pavel Salvetr, Pavel Novák, Jindřich Leitner, and Davy Deduytsche. "Mechanism of the Intermediary Phase Formation in Ti-20 wt. % Al Mixture during Pressureless Reactive Sintering." Materials 12, no. 13 (July 6, 2019): 2171. http://dx.doi.org/10.3390/ma12132171.

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This work aims to describe the mechanism of intermediary phases formation in TiAl20 (wt. %) alloy composition during reactive sintering. The reaction between titanium and aluminum powders was studied by in situ diffraction and the results were confirmed by annealing at various temperatures. It was found that the Ti2Al5 phase formed preferentially and its formation was detected at 400 °C. So far, this phase has never been found in this alloy composition during reactive sintering processes. Subsequently, the Ti2Al5 phase reacted with the titanium, and the formation of the major phase, Ti3Al, was accompanied by the minor phase, TiAl. Equations of the proposed reactions are presented in this paper and their thermodynamic and kinetic feasibility are supported by Gibbs energies of reaction and reaction enthalpies.

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33

Wang, Quan-De, Mao-Mao Sun, and Jin-Hu Liang. "Reaction Mechanisms and Kinetics of the Hydrogen Abstraction Reactions of C4–C6 Alkenes with Hydroxyl Radical: A Theoretical Exploration." International Journal of Molecular Sciences 20, no. 6 (March 14, 2019): 1275. http://dx.doi.org/10.3390/ijms20061275.

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The reaction of alkenes with hydroxyl (OH) radical is of great importance to atmospheric and combustion chemistry. This work used a combined ab initio/transition state theory (TST) method to study the reaction mechanisms and kinetics for hydrogen abstraction reactions by OH radical on C4–C6 alkenes. The elementary abstraction reactions involved were divided into 10 reaction classes depending upon the type of carbon atoms in the reaction center. Geometry optimization was performed by using DFT M06-2X functional with the 6-311+G(d,p) basis set. The energies were computed at the high-level CCSD(T)/CBS level of theory. Linear correlation for the computed reaction barriers and enthalpies between M06-2X/6-311+G(d,p) and CCSD(T)/CBS methods were found. It was shown that the C=C double bond in long alkenes not only affected the related allylic reaction site, but also exhibited a large influence on the reaction sites nearby the allylic site due to steric effects. TST in conjunction with tunneling effects were employed to determine high-pressure limit rate constants of these abstraction reactions and the computed overall rate constants were compared with the available literature data.

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34

Michalík, Martin, Ján Rimarčík, Vladimír Lukeš, and Erik Klein. "Thermodynamics of primary antioxidant action of flavonols in polar solvents." Acta Chimica Slovaca 12, no. 1 (April 1, 2019): 108–18. http://dx.doi.org/10.2478/acs-2019-0016.

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Abstract Very recently, a report on the antioxidant activity of flavonoids has appeared, where authors concluded that Hydrogen Atom Transfer mechanism represents the thermodynamically preferred mechanism in polar media (https://doi.org/10.1016/j.foodres.2018.11.018). Unfortunately, serious errors in the theoretical part of the paper led to incorrect conclusions. For six flavonols (galangin, kaempferol, quercetin, morin, myricetin, and fisetin), reaction enthalpies related to three mechanisms of the primary antioxidant action were computed. Based on the obtained results, the role of intramolecular hydrogen bonds (IHB) in the thermodynamics of the antioxidant effect is presented. Calculations and the role of solvation enthalpies of proton and electron in the determination of thermodynamically preferred mechanism is also briefly explained and discussed. The obtained results are in accordance with published works considering the Sequential Proton-Loss Electron-Transfer thermodynamically preferred reaction pathway.

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35

Singare, P. U., and A. N. Patange. "Study on Halide Ions Selectivity of Industrial Grade Anion Exchange Resin Auchlite A-378." International Letters of Chemistry, Physics and Astronomy 30 (March 2014): 44–50. http://dx.doi.org/10.18052/www.scipress.com/ilcpa.30.44.

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The thermodynamic approach was applied to predict the trend selectivity of industrial grade anion exchange resin Auchlite A-378 in chloride form towards iodide and bromide ions in the solution. The study was conducted by performing the Clˉ/Iˉ and Clˉ/Brˉ uni-univalent ion exchange reactions under gradually increasing temperature conditions. The thermodynamic equilibrium constants K values were used to calculate the enthalpies of the two uni-univalent ion exchange reactions. It was observed that the K values for Clˉ/Iˉ ion exchange reaction were higher than Clˉ/Brˉ exchange reaction under identical experimental conditions. Also the enthalpy values for the two uni-univalent ion exchange reactions were calculated as -39.51 and -18.38 kJ/mol respectively. The high K and low enthalpy values obtained for Clˉ/Iˉ ion exchange reaction is responsible for higher selectivity of the resin towards iodide ions as compared to that towards bromide ions, when both the ions are present in the same solution.

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36

Irving, Kenneth, Martina Kieninger, and Oscar N. Ventura. "Basis Set Effects in the Description of the Cl-O Bond in ClO and XClO/ClOX Isomers (X = H, O, and Cl) Using DFT and CCSD(T) Methods." Journal of Chemistry 2019 (February 26, 2019): 1–23. http://dx.doi.org/10.1155/2019/4057848.

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The performance of a group of density functional methods of progressive complexity for the description of the ClO bond in a series of chlorine oxides was investigated. The simplest ClO radical species and the two isomeric structures XClO/ClOX for each X = H, Cl, and O were studied using the PW91, TPSS, B3LYP, PBE0, M06, M06-2X, BMK, and B2PLYP functionals. Geometry optimizations and reaction enthalpies and enthalpies of formation for each species were calculated using Pople basis sets and the (aug)-cc-pVnZ Dunning sets, with n = D, T, Q, 5, and 6. For the calculation of enthalpies of formation, atomization and isodesmic reactions were employed. Both the precision of the methods with respect to the increase of the basis sets, as well as their accuracy, were gauged by comparing the results with the more accurate CCSD(T) calculations, performed using the same basis sets as for the DFT methods. The results obtained employing composite chemical methods (G4, CBS-QB3, and W1BD) were also used for the comparisons, as well as the experimental results when they are available. The results obtained show that error compensation is the key for successful description of molecular properties (geometries and energies) by carefully selecting the method and basis sets. In general, expansion of the one-electron basis set to the limit of completeness does not improve results at the DFT level, but just the opposite. The enthalpies of formation calculated at the CCSD(T)/aug-cc-pV6Z for the species considered are generally in agreement with experimental determinations and the most accurate theoretical values. Different sources of error in the calculations are discussed in detail.

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37

Prehl, Janett, Robin Masser, Peter Salamon, and Karl Heinz Hoffmann. "Modeling Reaction Kinetics of Twin Polymerization via Differential Scanning Calorimetry." Journal of Non-Equilibrium Thermodynamics 43, no. 4 (October 25, 2018): 347–57. http://dx.doi.org/10.1515/jnet-2018-0057.

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Abstract We present a kinetic model for the reaction mechanism of acid-catalyzed twin polymerization. Our model characterizes the reaction mechanism not by the reactants, intermediate structures, and products, but via reaction-relevant moieties. We apply our model for three different derivatives of 2,2’-Spirobi[4H-1,3,2-benzodioxasiline] and determine activation energies, reaction enthalpies, and reaction rate constants for the reaction steps in our mechanism. We compare our findings to previously reported values obtained from density functional theory calculations. Furthermore, with this approach we are also able to follow the time development of the concentrations of the reaction-relevant moieties.

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38

Trindle, Carl, and Kristin Romberg. "Reactions of HSCH2Radical with O2, NO, and NO2: Ab Initio Calculations of Enthalpies of Reaction." Journal of Physical Chemistry A 102, no. 1 (January 1998): 270–73. http://dx.doi.org/10.1021/jp972768k.

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39

Senthilkumar, K., S. S. Naina Mohammed, and S. Kalaiselvan. "Free Radical Scavenging Activity of Dihydrocaffeic Acid: A Quantum Chemical Approach." Asian Journal of Chemistry 33, no. 4 (March 20, 2021): 937–44. http://dx.doi.org/10.14233/ajchem.2021.23068.

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Based on density functional theory (DFT), to investigate relationships between the antioxidant activity and structure of dihydrocaffeic acid, quantum chemical calculation is used. The optimized structures of the neutral, radical and ionic forms have been carried out by DFT-B3LYP method with the 6-311G(d,p) basis set. Reaction enthalpies related with the hydrogen atom transfer (HAT), single electron transfer proton transfer (SET-PT) and sequential proton loss and electron transfer (SPLET) were calculated in gas and water phase. The HOMO-LUMO energy gap, electron affinity, electronegativity, ionization energy, hardness, chemical potential, global softness and global electrophilicity were calculated by using the same level of theory. Surfaces with a molecular electrostatic potential (MEP) were studied to determine the reactive sites of dihydrocaffeic acid. The difference in energy between the donor and acceptor as well as the stabilization energy was determined through the natural bond orbital (NBO) analysis. The Fukui index (FI) based on electron density was employed to predict reaction sites. Reaction enthalpies are compared with previously published data for phenol and 3,4-dihydroxycinnamic acid.

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40

Surpateanu, Gheorghe, Ileana Denisa Nistor, Ana-Maria Georgescu, and Neculai Catalin Lungu. "Syntone Chemistry. Theoretical study on the formation of glycine, alannine and serine." Revista de Chimie 70, no. 5 (June 15, 2019): 1707–11. http://dx.doi.org/10.37358/rc.19.5.7198.

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Three synthons: methylene, nitrene and carbon monoxide form aziridinone in the presence of molecular nitrogen at low temperatures. This one, in contact with the same three synthons could form the precursors of the first proteinogenic amino acids. This paper is a theoretical, thermodynamically and reactivity study concerning the formation of the three previously named amino acids at low temperature conditions. The key intermediates are identified in the formation of the three amino acids: aziridinone, aziridinonil and methyl-aziridinonil radicals. The quantitative results, enthalpies of formation, reaction enthalpies and free energies were taken from quantum mechanical calculations acquired by density functional method (DFT): B88-LYP.

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41

Surpateanu, Gheorghe, Ana-Maria Georgescu, Ileana-Denisa Nistor, and Neculai Catalin Lungu. "Synthone Chemistry. Theoretical Study on the Formation of Valine, Leucine, Isoleucine and Methionine." Revista de Chimie 71, no. 4 (May 5, 2020): 95–100. http://dx.doi.org/10.37358/rc.20.4.8047.

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According to synthonic theory of the formation of proteinogenic amino acids and of corresponding polypeptides, starting from three synthons (methylene, nitrene and carbon monoxide), four proteinogenic amino acids have been constructed: valine, leucine, isoleucine and methionine. This paper represents a theoretical, thermodynamic and reactivity study on the formation of the four previously mentioned amino acids at low temperatures. All the intermediates involved in the formation of these amino acids as well as the final products obtained by contact with water, an essential component of the Earth`s primary atmosphere, are specified. Quantitative data, formation enthalpies, reaction enthalpies and free energies were obtained in principle by DTF (B88-LYP) calculations.

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Plyasunov, Andrey V., Ingmar Grenthe, K. Simonsen, Shubhasish Mukherjee, Per M. Boll, William Errington, Carl Erik Olsen, et al. "Extrapolation of Enthalpies of Reaction in Electrolyte Systems to Infinite Dilution." Acta Chemica Scandinavica 50 (1996): 571–79. http://dx.doi.org/10.3891/acta.chem.scand.50-0571.

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43

Glazier, S. L., S. A. Odom, A. P. Kaur, and J. R. Dahn. "Determining Parasitic Reaction Enthalpies in Lithium-Ion Cells Using Isothermal Microcalorimetry." Journal of The Electrochemical Society 165, no. 14 (2018): A3449—A3458. http://dx.doi.org/10.1149/2.0761814jes.

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44

Ewig, Carl S., and John R. Van Wazer. "Ab initio reaction enthalpies for some gas-phase acid-base neutralizations." Journal of Physical Chemistry 90, no. 18 (August 1986): 4360–63. http://dx.doi.org/10.1021/j100409a029.

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45

Scheuring, Thomas, and Konrad G. Weil. "Mass Spectrometric Determination of Reaction Enthalpies in Some Alkali/Antimony Mixtures." Berichte der Bunsengesellschaft für physikalische Chemie 89, no. 7 (July 1985): 811–17. http://dx.doi.org/10.1002/bbpc.19850890718.

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46

Dorofeeva, Olga V., and Marina A. Filimonova. "Self-consistent enthalpies of formation of adamantanes by isodesmic reaction network." Journal of Chemical Thermodynamics 126 (November 2018): 31–37. http://dx.doi.org/10.1016/j.jct.2018.06.016.

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47

Zheng, Yan-Zhen, Geng Deng, Rui Guo, Da-Fu Chen, and Zhong-Min Fu. "DFT Studies on the Antioxidant Activity of Naringenin and Its Derivatives: Effects of the Substituents at C3." International Journal of Molecular Sciences 20, no. 6 (March 22, 2019): 1450. http://dx.doi.org/10.3390/ijms20061450.

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The radical scavenging activity of a flavonoid is largely influenced by its structure. The effects of the substituents at C3 position on the antioxidant activity of naringenin were carried out using the density functional theory (DFT) method. The reaction enthalpies related with the three well-established mechanisms were analyzed. Excellent correlations were found between the reaction enthalpies and Hammett sigma constants. Equations obtained from the linear regression can be helpful in the selection of suitable candidates for the synthesis of novel naringenin derivatives with enhanced antioxidant properties. In the gas and benzene phases, the antioxidant activity of naringenin was enhanced by the electron-donating substituents via weakening the bond dissociation enthalpy (BDE). In the water phase, it was strengthened by electron-withdrawing groups—via lowering the proton affinity (PA). The electronic effect of the substituent on the BDE of naringenin is mainly governed by the resonance effect, while that on the ionization potential (IP) and PA of naringenin is mainly controlled by the field/inductive effect.

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48

NAJAFI, MEYSAM, MOHAMMAD NAJAFI, and HOUSHANG NAJAFI. "THEORETICAL STUDY OF THE SUBSTITUENT EFFECTS ON THE REACTION ENTHALPIES OF THE ANTIOXIDANT MECHANISMS OF STOBADINE DERIVATIVES IN THE GAS-PHASE AND WATER." Journal of Theoretical and Computational Chemistry 12, no. 02 (March 2013): 1250116. http://dx.doi.org/10.1142/s0219633612501167.

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In this paper the reaction enthalpies of three antioxidant action mechanisms, HAT, SET–PT, and SPLET, for mono-substituted Stobadines were calculated in gas-phase and water. Results show that electron-withdrawing substituents increase the bond dissociation enthalpy (BDE), ionization potential (IP), and electron transfer enthalpy (ETE), while electron-donating ones cause a rise in the proton dissociation enthalpy (PDE) and proton affinity (PA). In comparison to gas-phase, water attenuates the substituent effect on all reaction enthalpies. Results show that IP and BDE values can be successfully correlated with the indolic N–H bond length after electron abstraction, R(N–H+•), and the partial charge on the indolyl radical nitrogen atom, q( N ). Furthermore, calculated IP and PA values for mono-substituted Stobadines show linear dependence on the energy of the highest occupied molecular orbital (E HOMO ) of studied molecules in the two environments. SPLET represents the thermodynamically preferred mechanism in water.

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49

Huang, Fang, Jinliang Jiang, Mingwei Wen, and Zhi-Xiang Wang. "Assessing the performance of commonly used DFT functionals in studying the chemistry of frustrated Lewis pairs." Journal of Theoretical and Computational Chemistry 13, no. 01 (February 2014): 1350074. http://dx.doi.org/10.1142/s0219633613500740.

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The benchmark study has assessed the performance of 18 density functional theory (DFT) functionals, including GGAs, hybrid-GGAs, meta-GGAs, and hybrid meta-GGAs, in predicting bonding strength, barrier height and structure for systems involving Lewis acids and bases. Three databases were built for the study, including 15 bonding enthalpies of dative bonds (DBH15), 10 reaction barriers (BH10) and 10 X-ray structures (XCS10). Wavefunction-based ab initio calculations were also carried out for comparisons. The benchmark data were computed at the CCSD(T)/BSI//MP2/BSI(BSI=aug-cc-pVTZ) level. The 6-311++G(d,p)(BSII) and 6-31G(d,p)(BSIII) basis sets were employed in DFT calculations. Generally, M06-2X/BSII and M05-2X/BSII outperform the other tested DFT methods. M05-2X/BSIII and M06-2X/BSIII are less accurate than M05-2X/BSII and M06-2X/BSII (or M05-2X/BSII//M05-2X/BSIII and M06-2X/BSII//M06-2X/BSIII), suggesting that large basis sets (e.g. BSII) are necessary to improve energetics. SCS-MP2 is less accurate than MP2, consistently overestimating bonding enthalpies and reaction barriers. Moreover, six DFT functionals (M05-2X, M06-2X, B3LYP, ωB97X-D, BMK and B97-D) were examined by comparing with the experimental bonding enthalpies of eighteen donor–acceptor complexes, which indicate that M05-2X and M06-2X are still better than others. Nevertheless, M05-2X and M06-2X significantly overestimate or underestimate the bonding enthalpies of F-substituted complexes, implying the necessity of improving the two functionals for describing fluorides. Using the six basis sets (BSI, cc-pVTZ, aug-cc-pVDZ, cc-pVDZ, TZVP and BSII) and DBH15 and BH10 databases, the influence of the basis sets on the performance of M06-2X functional was examined, which reveals that BSII is the most suitable basis set for the functional.

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Berbenni, V., A. Marini, and D. Capsoni. "Solid State Reaction Study of the System Li2CO3/Fe2O3." Zeitschrift für Naturforschung A 53, no. 12 (December 1, 1998): 997–1003. http://dx.doi.org/10.1515/zna-1998-1212.

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Abstract A thermoanalytical (TGA/DSC) and diffractometric (XRD) study has been performed on the solid state reaction system Li2CO3 -Fe2O3 in the x Li range 0.10±0.50. A detailed analysis of the results shows that the data are in agreement with a reaction model where the carbonate decomposition is regulated by the formation of both LiFeO2 and LiFe5O8 , and the relative amount of the two phases depends on the initial composition. The DSC evidence offers the possibility to directly quantify the LiFe5Ox phase. Furthermore it allows one to obtain the enthalpies of formation of both LiFeO2 and LiFe5O8 .

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